Method of manufacturing a viscose solution from wood-cellulose.



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mnrnon or MANUFACTURING A VISCOSE SOLUTION rnoivi WOOD-GELLULOSE.

No Drawing.

To all whom it may concern:

Be it known that I, Dr. ARNoLo BERN" STEIN, a subject of the German Emperor,

and a resident-of Chemnitz, in the Kingdom of Saxony, Germany,'have invented an linproved Method of Manufacturing 2. Viscose Solution from Wood-Cellulose, of whichthe following is a specification.

The object of this invention consists in the production of an imfproved viscose solution which is intended or the manufacture of I artificial silk, artificial films and similar 7 describe the method now generally employed. The cellulose is first placed inla articles.

The method at present employed, which consists in letting carbon bisulfid act upon alkali-cellulose, entails drawbacks which are overcome by the present invention. The principal drawback consists in the formation of undesirable by-products simultaneously with the intended xanthogenate.

In particular therefore my improved method consists in removing these .by-prod-' ucts, before the process of solution is completed and preventing their formation in the complete solution.

To make matters more clear, I shall briefly solution of caustic soda, containing about 18% of sodium hydrate and left there for 2-3 hours; it is then removed from the alkali and squeezed out until the weight ofthe alkali-cellulose is about 3 to 4 times the former weight of the cellulose. After the alkali cellulose has been left in closed vessels for 2 days, it is treated with carbon bisulfid, whereby the formation of the xanthogenate takes place. This can readily be dissolved I in a weak solution of vsodiuin hydrate and then forms the solution of raw viscose.

It has been mentioned already, that. the carbon bisulfid does not only produce the xanthogenate, but at same time some undesirable by-products, such as sulfocarbonates,

which impair the quality. of the final prodnot. This action of the carbon bisulfid is not confined to the process of treating the alkali I cellulose with the carbon bisulfid, but it con tinues in the raw solution of viscose, if the uncombined carbon bisulfid has not been completely removed before.

Various' methods havebeentr'ied, to obv Specification of Letters Patent.

Patented Dec. 22, 1914.

Applicatlonflled August 22, 1913. Serial No. 786,136.

scribed, is finely divided by means of a suitable device and transported into a rotary vessel, which may be similar .to a butter churn. An appropriate quantity of carbon bisulfid is added, anda'fter the Xanthogenate has been formed, the compound is conveyed into a vertical vessel provided with a stirring device and having a conical bottom, which contains a sieve and 'a stop cook. The vessel is filled with cold water, and the stirring device is put in motion. After a few minutesthe stop cockis opened, when a liquid of reddish color will flow out. The cold water used for washing the xanthogenate may contain a slight amount of an organic acid; for instance one half per cent. of acetic acid. This treatment does not merely effect the removal of a considerable part of the by-products from :the xanthogenatabut it has the further effect of acomplete removal of the uncombine d carbon bisulfid, wh'ich'is condensed by the coldwater and flows away with it. In this manner the formation of by-products in the purified viscose solution is prevented. The purified xanthogenate is next conveyed to the dissolving vessel, where a weak solution of sodium hydrate is addedand the complete viscose solution is formed. The simple process of washing thexanthogenate with cold water can be used effectually if the cellulose is derived from wood, because in this case no swelling takes place on the addition of water, as would be the case with xanthogenate from other kinds of cellulose, for instance if cotton is used.

The purifiedviscose solution, made manner described, has the advanta e that the threads'and other products, which are obtained in the precipitating bath, have a greater strength than those made from the raw viscose solution.

in the- What I claim as my invention and desire to secure by Letters Patent is:

I 1. The method of manufacturing a purified viscose solution from wood cellulose without the previous formation of crude viscose solution, consisting in washing with cold water the compound formed by treating alkali cellulose with carbon bisulfid, and

dissolving said compound in a solution of alkali.

2. The method of manufacturing a purifiedfviscose solution from wood cellulose I u l wlthout the previous formatlon of crude vlscose solution, consisting in washing with a cold non-alkaline aqueous liquid the com- 15' pound formed by treating alkali cellulose with carbon bisulfid, and dissolving said compound in a solution of alkali.

In testimony whereof I alfix my signature in presence of vtwo witnesses.

' DR. ARNOLD BERNSTEIN.

\ Witnesses:

EMIL S'IEJER,

WALTER KOEHLER. 

